The goal of the proposed work is to utilize electrophysiological and psychophysical techniques as a means of studying those mechanisms of the human visual system in the normal and diseased state which pertain specifically to pattern (spatial) vision. The research program includes: (1) The electrophysiological recording of the visually evoked potential (VEP) using a pattern stimulus and the use of psychophysical measures (preferential looking behavior - PLB) to follow the development of pattern vision in preterm and term infants; and to use these data to determine when the human visual system matures and when critical periods occur; (2) Recording of VEPs and the psychophysical measurement of vision in infants and young children who have been visually deprived because of congenital cataracts, strabismus, anisometropia, ptosis and corneal opacities in order to measure the rate of development of pattern vision in the affected eye(s) and to establish critical periods for treatment. (3) Recording of the electroretinogram and VEP in adults with macular and optic nerve disease using a patterned stimulus as a means of differentiating between macular and optic nerve disease. These data will aid in determining how spatial vision is affected in the diseased state and increase our general understanding of the basic mechanisms underlying spatial vision in the normal visual system.